RedEaredSlider writes: Earlier this year, Facebook and Twitter played a crucial role in mobilizing protestors in Iran, Cairo and Tunisia. Now Tumblr has been uniquely appropriated for a U.S.-based protest movement known as Occupy Wall Street, which has been coalescing in New York, Boston and Chicago to challenge the influence of corporate money on government and the growth of social and economic inequality.

A hybrid of ordinary blogging platforms, such as Typepad or Wordpress, and of the microblogging site Twitter, Tumblr gives users the ability to post photos, videos and messages and share with people they don’t know.

The site has been a force behind the Occupy Wall Street protests, growing the number of demonstrations from just dozens of people in late September to thousands on Wednesday, as several local unions joined in on a march down Broadway.